State Health Officials Announce Additional Human Cases of
West Nile Virus in Massachusetts
West Nile Virus risk levels now elevated in eight more communities, including Ashland which has been elevated to High.
On Friday, September 5, 2025, the Massachusetts Department of Public Health announced two additional human cases of West Nile virus (WNV) in Massachusetts this year. One is in Hampden County, and the other is in Middlesex County.
These cases bring the total number of confirmed WNV infections this season to four. As a result, risk levels for WNV have been elevated to high in Ashland, Framingham, Marlborough, Natick, Sherborn, Southborough, Sudbury, and Wayland.
Infections can continue to occur until the first hard frost of the season which is likely still many weeks away. We are encouraging everyone to continue to take the necessary steps to protect themselves from mosquito bites, including by using mosquito repellent, wearing long sleeves and pants to reduce exposed skin, and to drain anything that may be collecting water outside your home.”
The risk for WNV is now high in 28 municipalities in Middlesex, Essex, Suffolk, and Worcester counties and moderate in 175 cities and towns in Barnstable, Berkshire, Bristol, Essex, Franklin, Hampden, Hampshire, Middlesex, Norfolk, Plymouth, Suffolk, and Worcester counties.
In addition to WNV, Eastern Equine Encephalitis (EEE) has also been detected in mosquitoes in Massachusetts this year. There have been 21 EEE-positive mosquito samples and no human or animal cases so far this year.
Surveillance information, including cases, will continue to be updated on a daily basis and posted online at Massachusetts Arbovirus Update. DPH encourages everyone to use this online resource regularly to stay up to date on risk levels in their community and around the state.
People have an important role to play in protecting themselves and their loved ones from illnesses caused by mosquitoes.
AVOID MOSQUITO BITES
APPLY INSECT REPELLENT WHEN YOU GO OUTDOORS.
Use a repellent with DEET (N, N-diethyl-m-toluamide), permethrin, picaridin (KBR 3023), IR3535 or oil of lemon eucalyptus [p-methane 3, 8-diol (PMD)] according to the instructions on the product label. DEET products should not be used on infants under two months of age and should be used in concentrations of 30% or less on older children. Oil of lemon eucalyptus should not be used on children under three years of age. Permethrin products are intended for use on items such as clothing, shoes, bed nets and camping gear and should not be applied to skin.
CLOTHING CAN HELP REDUCE MOSQUITO BITES.
Wearing long sleeves, long pants and socks when outdoors will help keep mosquitoes away from your skin.
BE AWARE OF PEAK MOSQUITO HOURS
The hours from dusk to dawn are peak biting times for many mosquitoes. When risk is increased, consider rescheduling outdoor activities that occur during evening or early morning. If you are outdoors at any time and notice mosquitoes around you, take steps to avoid being bitten by moving indoors, covering up and/or wearing repellant.
DRAIN STANDING WATER
Many mosquitoes lay their eggs in standing water. Limit the number of places around your home for mosquitoes to breed by either draining or getting rid of items that hold water. Check rain gutters and drains. Empty any unused flowerpots and wading pools and change water in birdbaths frequently.
INSTALL OR REPAIR SCREENS
Some mosquitoes like to come indoors. Keep them outside by having tightly-fitting screens on all your windows and doors.